The present invention relates to an apparatus for electro-optically reading an original, and more particularly to an original reading apparatus used for inputting image information into various instruments such as, for example, a digital copying machine, an intelligent facsimile, a personal computer or any other work stations.
Most of the conventional original reading apparatuses of this type are of such a type that an optical system is arranged on the underside of a surface of an original which is to be read out and reads the original from below. For instance in case of a facsimile, an original sheet is delivered over a reading sensor with its surface to be read being directed downward. Also, in case of a copying machine, an original is laid on a transparent original platen with its surface to be read being directed downward, and then a reading scanner is moved to read the original.
On the other hand, for example, Japanese Patent Unexamined Publications Nos. 55-40758 and 59-41963 show original reading apparatuses of the top side reading type in each of which an optical unit is disposed on the upper side of an original. The former publication proposes a reading apparatus in which the original sheet is delivered with its surface to be read being directed upward while being illuminated, and its reflective light is photoelectrically converted by light receiving elements to read its image information. The latter publication is directed to an original reading apparatus in which the original is laid with its surface to be read being directed upward, and is read by a head scanning thereabove. This system is so designed as to exactly read out the information even if the position of the surface of the original to be read is at a high level.
Furthermore, the top side reading systems with a surface of an original to be read being directed upward are shown or disclosed in Japanese Patent Unexamined Publications Nos. 55-157761, 55-157763 and 55-157764.
The recent development of personal computers, engineering work stations and the like has been advanced at a good pace. In these apparatuses, the performance and function for creating figures and images under the control of computers, and for forming documents including the figures and images at random by means of its word processing function have been enhanced. But there is still a limitation for rapidly forming, as desired, the figures or images with these apparatuses. Therefore, there have been increased demands for introducing image information into these apparatuses from the outside.
It is, however, difficult to code the image information unlike the literal information in addition to the fact that the image information have a large amount of information. For this reason, it is necessary to provide a large capacity of memory for processing the image information, which would lead to increased cost and a time-consuming processing, resulting in a deterioration in the operability. Thus, unnecessary image information must be excluded as much as possible. This would lead to simplification of a structure of the overall system to improve the operability. Accordingly, it is very important to read, with an original reading apparatus, only a portion of an original that is truly necessary, in such a manner that a necessary minimum processing work will be carried out after the readout.
In an original reading apparatus of the bottom side reading type, it would be substantially impossible to partially read out an original without effecting any direct work on the original, such as covering the unnecessary parts of the original with a blank paper.
In view of this, Japanese Patent Unexamined Publication No. 60-213168 shows a system for a conventional copying machine of the bottom side reading type. In this system, a number of electrical switches are arranged along adjacent sides of an original platen. When the partial reading of an original is desired, the corresponding switches to opposite ends in a longitudinal direction and opposite ends in a transverse direction of the position to be read are to be depressed, thereby inputting the partially assigned region of the original into the system. Incidentally, in this system, special lamps are provided to illuminate the original from below so as to indicate the image pattern transparently on the opposite surface of the original for configuration of the assigned region. However, as the image to be viewed by the operator is inverted, it would be difficult to confirm the assigned region.
Particularly, in case of an original having information of letters, figures and/or images on both faces thereof, these letters, figures and images would overlap to one another transparently through the original sheet, and thus it would be extremely difficult to confirm the assigned region. Also, since the system is such that the opposite ends both in the longitudinal and transverse directions of the partial region of the original are assigned, there is limited the partially reading to only a rectangular shape or a simple polygonal shape.
In the above-described Japanese Patent Unexamined Publication No. 59-40758, the surface of the original to be read is directed upwardly, so that it is possible to view the contents of the original from above. In this publication, there is a description that the partial readout of the original is possible by setting the original in a state where the original is moved in a midway and then starting the readout operation. However, in such a system, it is unclear whether or not the desired portion of the original exactly corresponds to the light receiving elements. Thus, it is impossible to expect to ensure the satisfactory accuracy.
Furthermore, in the apparatus proposed in the above-described Japanese Patent Publication No. 59-41963, the surface to be read of the original is directed upwardly and it is possible to read an original such as a book having a physical thickness. Therefore, it is possible to change pages of the original under the condition where the original is set in the apparatus. Also, in respect of the partial reading operation, it is easy to perform the works of covering from above, with a piece of blank sheet, an other portion that is unnecessary to read, or of overlapping a plurality of originals for composite readout, as compared with the bottom side reading type apparatus. Nevertheless, also in this case, it is difficult to partially read the original with high accuracy and the manual work for this end is time-consuming.
In addition, in order to read the image information for the necessary minimum processing, it is necessary to lay the original on a reading apparatus with high accuracy. However, in the conventional apparatus, although it is possible to roughly correct the positional offset of the original, there is almost no reference for the exact position of the original. As a result it is difficult to correct or compensate for the positional offset or displacement of the original.
For example, in the case where an edge of the original sheet is aligned with an associated edge of the original platen, it is possible to input the information without any correction if the contents of the original is not slanted or inclined with respect to the original sheet. But, if the contents is inclined the original sheet, it is necessary to incline the original sheet in the reverse direction to compensate the inclination of the contents of the original. In this case, there comes to be no reference. Also, even if the original is not inclined, when the edge of the original sheet is aligned with the platen edge, there is a fear that the part of the original to be inputted would come out of the possible input range of the apparatus.
Thus, there are problems that it is time-consuming and troublesome to read out the original while slightly displacing the position of the original and to select the optimum read-out among those read at the plural positions, and the processing would be complicated in the case where the read information is shifted or rotated by controlling means of a personal computer, a word processer or the like.